Interaction of HCl vapor with water‐ice: Implications for the stratosphere

Abstract

The nature of the interaction of HCl vapor with ice has been investigated, using thermal analysis and FTIR spectroscopy to characterize the ice substrate, and mass spectrometry to measure the concentration of HCl and H2O vapors in the gas phase. The results indicate that a liquid layer is formed rapidly at the ice surface for ice exposed to HCl vapor at partial pressures above those characteristic of the ice‐liquid (aqueous HCl solution) equilibrium system. This liquid layer also forms below the eutectic temperature (186 K); that is, it forms even at temperatures at which the liquid is metastable with respect to the formation of HCl trihydrate. For smaller HCl partial pressures such as those prevailing in the stratosphere, the HCl is taken up by the ice surface in amounts corresponding to a large fraction of a monolayer. The chemical reactivity of this surface HCl is very large: Chlorine activation by type II polar stratospheric clouds (consisting of ice particles) should occur efficiently by reaction of the HCl with ClONO2.

A surface chemistry model for nonreactive trace gas adsorption on ice: Implications for nitric acid scavenging by cirrus

“…In the analysis described here we assume a dissociated rather than a molecular state for HNO 3 and/or HC1 adsorbed on ice in agreement with laboratory studies, indicating that both HC1 and HNO3 ionize on ice surfaces [Abbatt et al, 1992; Zondlo et al, 1997]. For clarity of presentation the preexponential factors for the adsorption and desorption rate constants are simplified compared to the relations given in Tabazadeh and Turco [1993].…”

Supersaturation, dehydration, and denitrification in Arctic cirrus

“…Experimental evidence exists for the fact that growing ice surfaces lead to enhanced uptake of HCl (Abbatt et al, 1992;Huthwelker, 1999). Very recently, evidence was found for significantly enhanced uptake of HNO 3 by growing relative to static ice films (J.…”

Interaction of Hydrogen Chloride with Ice Surfaces: The Effects of Grain Size, Surface Roughness, and Surface Disorder

“…The resulting water vapor pressure versus temperature curve agreed well with that reported by Marti and Mauersberger. 108 Three types of ice samples were used in this study: smooth ice films formed by quickly freezing from the melt, 109 vapor-deposited ice films, 10,110 and zone-refined ice cylinders. 107 For ice preparation details, please refer to the SI.…”

“…HCl has been found to be the most abundant chlorine reservoir during PSC events, and its reaction with ClONO 2 on ice is thought to be the most important of the chlorine activation reactions: 2 The reaction probability, γ, of reaction 1 on ice has been found in multiple laboratory studies to be high (γ > 0.1) 2,4-10 and independent of HCl partial pressure (P HCl ), even when experiments cross the ice-liquid phase boundary into high HCl partial pressures which are known to induce melting of the ice sample. 10 Clearly, characterization of the interaction of HCl with ice is one of the first steps toward understanding chlorine activation. Over the past 25 years, the HCl-ice system has been investigated using numerous experimental 2,4,6,10-71 and theoretical approaches.…”